As mate was getting out of a current-model full-NitrilonTwist 2 the part of the boat under a jetty rose up into the sharp end of a bolt securing a mooring ring.
.. a two-and-a-half foot rip tore across the top of the hull in both directions with a puff of South Moravian talc. As it’s a largely linear rip in an accessible location, making the repair was fairly straightforward: sew, then patch.
[FYI: I know of two other Twists which have suffered similar long rips: here and here. But not any other Gumotex model].
Because the coated core of the red Nitrilon fabric is a woven mat, sewing is an effective way of holding the two sides of the rip together to reduce the tension on the eventual glued-on patch once the boat is inflated. You need an awl spike to pre-poke each hole for the thick polyester thread. This fabric is hard to cut with sharp scissors, let alone thread with a needle.
Rip neatly sewed up with a special cobbler’s reverse herring backflip cross-stitch. One thing that got forgotten was sanding then cleaning the surfaces alongside the rift before sewing began.
Completed repair. This would work on a PVC IK too, but most of them are shell and bladder or drop-stitch. PVC is a bit harder to glue well.
You can get Chinese PVC D-rings dirt cheap on eBay but genuine hypalon D-rings (not PVC claiming to work on hypalon) cost a lot for what they are. Once you factor in the price of two-part glue, it adds up, especially if you have a few to fit. It’s fairly easy to make your own D-rings for your IK to attach gear, thigh straps, footrest mounts and so on.
You can buy metal D-rings by the sack-load online, as well as round PVC or Hypalonpatches. (‘Hypalon’ is pretty much the same synthetic rubber as Gumotex Nitrilon and Grabner Nordel). Or buy an off-cut (above right) for much less and cut your own. A D-ring doesn’t have to be round but it’s better if corners are rounded. You will notice how unusually hard it is to cut this stuff with scissors or a blade. The fibre core is tough: good for zero-elasticity in an IK.
Pictures below show how to make your own D-rings. Go to this page for how to apply any patch, step-by-step.
Sticking to the Rules I needed to fit some tube-top D-rings to properly support a second backrest in my Sunny 2020. I found a stray, opened tin of Bostik 2402 two-part in my kit bag, but with an expiry date of 2009. Back then I only owned this original Sunny and looking it up, 2402 turned out to be for rubber boats. Perhaps I bought it more recently but didn’t notice the expiry date. In the tin the glue was still liquid and unseparated, but the little bottle of Bostik D-10 hardener had long since evaporated. Digging around, I also found an opened bottle of PolyMarine hardener. Comparing chemicals showed they both contained Diphenylmethanediisocyanate, one of the few words that’s too long for a Scrabble board. I mixed the wrong-brand hardener with the 11-year old glue 25: 1 and the bond looked as good as anything.
Hypalon is a cool-sounding word and although not made anymore, has become a generic term for the similarly durable syntheticrubber-coated fabrics still in production, like Nordel and Nitrilon. Once upon a time all rafts and were made of hypalon, then less expensive Asian PVC came on the scene. More about IK fabrics.
The other day, while lashing the Seawave to a chopped-down trolley, the bag sagged under its own weight and rubbed on the sharp edge of the hard plastic wheels which wore through the pack and then the boat’s hull (left) ;-((
The trolley had worked fine with my UDB drybag in New Zealand (below left), but that was partly because you can fully inflate a UDB via its one-way oral valve, transforming it from saggy sack to firm travel sausage.
Ironically, just two days before I damaged my Seawave I’d snagged a BNWT Orlieb RS140 (right) on ebay. I’d been eyeing up this non-rigid wheeler duffle for a while as a versatile Seawave transporter plus a reliable on-water drybag/buoyancy aid. With a bag like this, an IK or whatever you got can be transported easily across any wheelable terrain, or carried as a holdall or on its backpack straps if you’re strong enough.
With enough practice applying D-rings, let along bike and moto punctures over the decades, I was confident I could do a bomb-proof repair on my Nitrilon Seawave. In a way, I was even a little chuffed that my 5-year old IK was earning its first battle scars. Plus, in my experience rubber-based IKs like Gumotex, NRS and Grabner glue more reliably than PVC boats. Shiny packraft TPU is even easier: you can just tape it, but packrafts are low-psi boats not normally inflated with mechanical pumps. My adapted Seawave side tubes run 4 or 5 psi.
Things you will need
Patch The right two-part glue (below left) Solvent (MEK, Toluene) and rag Sandpaper or abrasive foam sanding block (note: Toluene eats foam plastic sanding blocks) Masking tape Small brush or wipe-stick Tyre repair roller (right) Well ventilated space to do a good job
The basic gear you need for packrafting adventures so you don’t end up as above, or simply just inconvenienced and wet. For general camping kit (sleeping, eating, washing) you’ll find lists all over the internet and beyond. Mixing paddling with walking, I prefer a 1-kilo down bag, a compact tent, a thick, full-length air mat and a Pocket Rocket-like burner with a big Tatonka or MSR 500ml+ pot/cup. Below, I suggest cheap alternatives in green. A cheap alternative to a proper packraft is of course… a Slackraft but you’ll only every buy one once ;-)
1. A pack for your raft
Do you use a regular hiking backpack packed with your boat in or outside, or a purpose-made drybag pack with usually a rudimentary integrated harness, or use a separate packframe harness as pictured?
If you’re a first timer and own a regular hiking backpack, make do with that, but having tried both I prefer a harness. You’re on the water so (unless you can store in the hull, waterproofness trounces all-day carrying comfort. A submersible UDB duffle is tougher and as airtight as a packraft and provides high-volume back-up flotation should you get a flat on the water; important and reassuring.
For short approach walks like on the Tarn, or theKimberley, I used the UDB’s basic integrated harness: just sewn-on straps. For Turkey which was mostly walking, I fitted it into NRS pack harness (above left and right; no longer made) whose capacity easily exceeds its straps and your back. In Germany Anfibio Packrafting now sell the more sophisticated Six Moon Flex Pack (left; new 2021 design), a ‘drybag hauling system’. You can lash anything that fits within the straps, including your rolled-up boat. ULA Epic is another one. In Europe the packraft harness seems unknown. Remember: with any big backpack the key to support and comfort is a stiff board or frame connecting the hip belt and shoulder strap mounts so the weight can be carried low on your hips, not hanging from your burning shoulders.
Cheap alternative: any old rucksack and a tough bin bag.
2. Four-piece paddle
Get a paddle that breaks down into four pieces for easy transportation. A paddle like this may not be as stiff as a good two-piece, but the Aqua Bound Manta Ray left or the Anfibio Wave (right) will still be under a kilo and anyway, you’re in a slow packraft not a razor-thin surf ski. Some four-parters don’t like being left assembled when wet; don’t leave it more than a couple of days or it’ll be hard to separate.
Even cheap alloy-and-plastic ‘shovels’ come with adjustable feathering; an ability to offset the blades. Flat (zero offset) works OK, but most find a bit of offset makes paddling more efficient. I’ve got used to 45° Right (right blade rotated 45° forward) over the years. Left handers will go the other way. The Anfibio Wave had infinite feathering and 10cm length adjustment.
Cheap alternative: A TPC 2-piece or similar.
3. PFD (‘personal flotation device’)
A proper foam pfd is bulky in transit but is essential for remote solo paddles or white water (as is a helmet if you’re really going for it). For flatwater paddles and calm, warm conditions Anfibio’s lightweight inflatable Buoy Boy (left) has twin inflation chambers, rolls down to less than a litre in volume and comes with handy net pockets and a useful crotch strap to stop it riding up when you’re flailing around in the water, but at any other time, you’ll barely know you’re wearing it. Note It doesn’t claim to be a CE-rated buoyancy aid
Cheap alternative: A used foam PFD.
4. Wet shoes I’m on my second pair of Teva Omniums (left) which are do-it-all wet shoes that are OK for walking too. If trekking the wilderness for days with a full pack over rough terrain, you’re better off with proper lace up trail shoes or boots, but bear in mind that anything with a breathable membrane takes ages to dry once soaked inside out. I use membrane-free desert boots. SealSkin socks are another solution, while they last. More here.
Cheap alternative: Old trainers or Crocs.
5. Day bag or case
You want something light to carry your valuables when away from the boat in populated areas. Choose a bag or case which fits under your knees without getting in the way. Whatever it is, it will sit in water, get splashed or even submerged, so it needs an airtight seal. If it has handy external storage pouches or pockets, so much the better.
Recently in France I tried an Underwater Kinetics box (22cm x 16 x 8; 540g, above left) used on ebay for under a tenner. It’s about the size of a Peli 1150 but a bit less deep and took my Kindle Fire, camera, wallet and bits. It’s light enough to carry away from the boat and also happens to make a handy camera stand. But most of the time I use a 20-L Ortlieb Travel Zip (left) which zips open easily and stores loads. As for a camera? This is what you want.
Cheap alternative: large, clip-seal lunchbox and a plastic bag.
6. Repair kit
A couple of feet of Tyvec or similar tape and a small tube of Aquaseal is probably all you need for quick repairs. Something I’ve never had to do in years of packrafting.
Michael S from BC came up with a good idea for securing stuff, seats or thigh straps to the floor of your IK without resorting to the faff gluing on D-rings – something that takes application and the right glue to do well. He suggests the cavity formed between the floor and the sides when you pump an IK up can be used to jam in short tubes attached to tape loops. Example left is a Sea Eagle Full D-S, but I know Gumotex and other IKs I’ve owned have a similar space along the sides.
Pictured below are some Sherpak Quick Loop tie-downs which go from $15 a pair on amazon US. You can buy Thule ones for six times as much or search eBay for <Kayak Hood Trunk Tie Down Loops> sent from China for 7 quid. The idea is you shut them under your car’s bonnet, tailgate or doors (right) to help lash on stuff including boats.
But they could also be lodged in an IK’s floor/side cavities as you pump up, and of course can be positioned anywhere and slid forward or back. It’s possible the 1-inch diameter tubes shown may be too small and pull out, so make your own using larger conduit from a hardware store, or just a shore-side stick and washed-up rope. Below: I made my own. To be tested. Neato mosquito as my Kiwi mate used to say.
Performing my cutting-a-kayak-in-half trick gave me a long overdue chance to see exactly how they’re put together, as well as other stuff, like why it was failing and how well certain glues stuck.
The neoprene inside I used to assume it was the same coloured coating inside the boat as out; it’s just simpler. But of course, the diagram left is clear: what’s outside and what’s inside an IK hull is not the same stuff. There’s no need to waste UV-resistant hypalon coating (or colouring or that matter) inside the boat’s benighted chambers. All it needs to be is the same durable and airtight coating, and neoprene – the brown rubber-like coating left – does that fine. I bet I’m not the only one to mistake ‘neoprene‘ as simply that closed-cell sponge used in wetsuits or laptop sleeves. In its solid form it’s a durable synthetic rubber, but I presume lacks the full-on UV resistance of hypalon which DuPont invented shortly after.
I-beam floor As mentioned here, an inflated vessel will seek equilibrium by attaining a rotund form, be it tube or sphere. A flat inflated plane such as an airbed or an IK floor needs to be a series of parallel tubes – or just a non-inflated sheet, like packraft and white-water raft floors. It also works the other way with bed mattresses. The springs and foam must be constrained by straps or whatever to keep the spring mattress flat. So this is an IK I-beam floor (left): probably the same tough core of nylon or polyester scrim, but without the impermeable hypalon and neoprene coatings of the exterior panels. Note the pre-folds or creases to help the Semperit pack flat. I imagine modern IKs do the same, but it all explains the necessary attention to detail which makes ‘tubeless’ IKs like this so labour intensive, compared to ‘bladder’ designs like Aire.
Twin side-tube IKs like this Forelle, the Incept and Grabner Holidays, have two smaller tubes one on top of the other, rather than one fat side tube like my Seawave (left, red) or Amigo. It gives the same buoyancy, more freeboard (above water height), a slimmer profile (more speed) or make more volume inside (easier packing). The red Seawave on the left is 82cm wide; the Semperit is 72. It makes the boat look a whole lot better too and overall because it’s also no less stable, I’d say it’s the best design for an IK, but it also needs I-beam sections to constrain the two side tubes.
I can’t say I could suck air through the scrim easily, but I’m pretty sure it’s porous – I didn’t find any transfer holes to allow air to flow between adjacent tubes – they might be a weak point. When an IK like this is over-inflated (or left in the sun) and is unable to purge through PRVs (none on the Semperit), you imagine it’s this scrim which either tears apart, most probably at the T-join where it’s glued to the neoprene. I tried tearing sections of scrim by hand; impossible where it was uncut, but as soon as you nick it with a knife it would tear quite easily, like thin cotton cloth. This fabric was at least 40-years-old and had one or two patches of mildew, but was still tough and the whole assembly of the boat has held together amazingly well over the years.
Where mine failed Inspecting the fatal second leak alongside the earlier repair, it seemed air was pushing through where two sections of I-beam scrim butted against each other. Perhaps the old coatings stretched differentially here or were just worn out. It did look like the hypalon was simply flaking away. I could have fixed that leak but, as mentioned, another would probably pop up whack-a-mole style somewhere else, quite possible while at sea in either my- or a new owner’s hands.
Glue test I repaired the big original ‘L’ tear with a 5″ round patch of hypalon and two-part glue (above and left). I then patched a down-to-the-scrim scratch under the hull with one-part Bostik 1782 (left). I used the same glue to repair the initial new leak inside (bubbling water, above).
Although I’m pretty sure they’d have lasted, I could easily pull off the Bostik patches by hand. Pulling off the big round Polymarine’d patch was another matter. It just so happened I’d sawn through the round patch but, only once I got some pliers under a lip (above left) was I able to separate it from the hull. As you can see in the big image below, either the ancient orange hypalon coating of the IK, or the newer red hypalon of the patch separated from their respective nylon cores – the glue’s bond was stronger than the actual hypalon coatings, new or old.
I get a bit lazy about having to faff about with two-part glue, and I also wonder if I ever guestimating the 25:1 ratio correctly. But as you can see, this stuff sticks. If you absolutely, positively want it to stay stuck, use two-part adhesives. I still don’t know if the second part curing agent merely speeds up the drying process, or is chemically integral to creating the very strong bond. I’d think it’s the latter, otherwise why bother.
Other stuff The distinctive marine plywood bow has lasted fine – no warping at all and the rivets are still intact. It may have been an early design solution to easily joining the three sections of the hull in a nice sharp point, though they managed that join easily enough at the back. Maybe it was as much for protection and a frontal tracking aid. I now have enough hypalon patches and D-rings to see me out. Other images from the autopsy below.
A couple of days after trying out the Semperit I noticed a scratch on the hull bottom (left) so decided to pre-emptively patch that with Bostik 1782 (less faff than 2-part). It looked like an old scratch which had opened up by reusing the boat. I reinflated a day or two later, but a few days on noticed the floor was flat. I pumped it up again – air was hissing from a crack in the hypalon coating inside the boat, more or less under the seat (below; colours enhanced for clarity).
This seemed a bit odd. The boat hadn’t been over-inflated or left in the baking sun, and there wasn’t any obvious rubbing in the two hours I’d used it, though I suppose this is a high-wear area and an old boat.
I suspected general, age-related delamination or entropic porosity. The outer orange hypalon coat can be rubbed or scratched down to the fabric core, as with the hull scratch I’d just repaired. But inside should be an airtight layer of neoprene. There’s no way of checking that without open boat surgery. To be honest, it’s what I half-expected from a 40-year-old IK, which is why I’d kept the refurb and expenses to a minimum. I suspect sudden use after many years possible neglect had accelerated decay. I see the keel-strake is coming away too, as are some other black patches holding the rusting D-rings.
I’ve experienced similar deterioration when buying old vehicles for long trips. They seem like a bargain and have a solid ‘they-don’t-make-’em-like-they-used-to’ reputation. But reviving them, or just asking them to perform as they once did, can lead to a string of failures until it’s just not worth it (left). Much depends on how they’ve been maintained over the years. I recall writing in one of my books (or maybe on here): “you can’t give your old gran a pair of trainers and expect here to run a marathon without having a heart attack“.
I patched the wear-hole with more 1782, reluctant to waste good two-part PolyMarine. I pumped up and filled it with water: all good, but an anomalous perforation somewhere else can’t be ruled out. That’s another thing I’ve learned with old cars and bikes: you replace the clapped-out engine then the clutch goes; you replace the clutch and the gearbox goes; you replace the gearbox and so on… The strain of refurbishment gets passed on to the weakest point, and when that’s repaired, to the next weakest point. An IK will get you to shore on two chambers, especially if it’s just the floor that’s gone. I had that once with the Incept. Out with your pals on a warm summertime river that’s no drama. Elsewhere, alone with the wind picking up; not so trivial.
Years later I learned PolyMarine make SealFlex – a latex sealant (right) to revive old inflatables, PVC or plastic. You pour some in each chamber and roll the boat around for a couple of days. It costs £26 posted for 500ml – possibly worthwhile on your cherished RIB; not so sure on this old IK but had I known of it I may have given the old Trout a pint’s dose. After that you’ve got to know when to call it a day, and that day may have come. It might be fine for a guest or a rec river boat, but I don’t do so much of that nor have space for more stuff than I need.
A few hours later the floor was soggy – this time it had let go a few inches up from the recent patching. Up to then I’d been considering putting it back on ebay with a clear semperit caveat emptor. But then I decided sawing it in half would be more fun and educational. I always wondered what exactly an I-beam floor looks like. More here.
Here in the Summer Isles the reliable May sunny spell is about to end. It’s been great for solar panels with strong afternoon easterlies, not so good for day-long IK-ing. Suilven mountain even caught fire. Yesterday, before it picked up we nipped out in the Seawave to Eilean Fada Beag (below) and listened to the birds. By the afternoon it was blowing hard.
High time to patch up my latest IK: an old Semperit Forelle 2 I picked up in Cornwall. The boat was sold with some classic paddles which went straight in the bin, as well as a big tear in the side (right). Plan is to patch that hole, then see if it still holds air.
Semperit is an Austrian tyre manufacturer who’s still in business. Afaik, their IKs were a bit of a short-lived rubbery diversion in the 1960s. If my 40-year-old boat has no other more awkward leaks, I’ll rig it up and take it for a spin. But first, I scrubbed off a couple of decades of crud and let it dry.
I wondered about sewing up that L-tear before patching it – the Forelle’s hypalon seems pretty thin, but decided to just slap on a 5-incher. I’ve glued on loads of accessory patches but have never actually had to repair a hole in a hypalon IK in all these years. So I took note of the NRS repair video here: rough up hole and patch: wipe clean with solvent; apply two coats of glue and when knuckle dry apply the patch and roller the living daylights out of it.
Watching that vid, I saw they used a much better tool for pressing down patches; an ash-handled Sealey TST15 tyre patch roller, unless I’m very much mistaken. The knurled metal wheel embedded in the wooden handle can lay down much more pressure than the wide plastic lino roller I’ve been using. Just before I did that, it occurred to me stray glue may squeeze through the tear and glue the insides together. Don’t want that nein danke so, with no better ideas, I stuck a bit of paper in there. Seems to have worked.
With glue left over, I thought I may as well stick on couple of floor patches for a seat base and a footrest tube. As these are non-critical fittings I used any old D-rings I had: a woven nylon one and probably a PVC. I’ve glued PVC to hypalon before for other fittings.
With them in place I couldn’t resist rigging up the old Trout with a rope-and-pipe-lagging backrest, an old Alpacka packraft seatbase; a drainpipe footrest tube and a lead. All stuff I happened to have in my IK box of bits or found in the barn among the rat droppings. I jury-rigged the K-Pump for nozzeling but haven’t pumped it right up to 2psi as I’m letting that big patch cure for a bit.
Looking round the repaired boat I see it has rudder mounts; not sure I’ll need one on a 3.56m boat. There are six D-rings on top of the double side tubes but they don’t look like they’ll take the backwards strain of a fabric backrest Forelles came with wooden backrest bars, (like Grabners who took over Semperit) and which I’ve found prone to bending when used with a firm footrest tube.
There’s also a squished up full-length keel strip along the bottom. If it works for tracking it will be nice not to have the usual skeg-grounding aggro in shallows or on land. But maybe that keel will slow down turning which is why they have the rudder attachment? We shall see. With twin side tubes the Forelle is just 70cm wide – that’s <28″. But with a thin floor and me sat low in the high sides I’m sure it will be stable enough. Gumotex still use them for their seats, but the ‘lilo plugs‘ on the three chambers are a bit of a faff for getting a good charge of air.
If the Semp proves viable, I may replace them with proper IK valves. Or I may just leave them as they are. Three £15 Gumotex valves + a £20 PRV will cost the same as the boat, and the lilo plugs can be regarded as their own ‘total loss’ PRVs – when the boat gets too hot they pop! And anyway, there’s no room to fit a big IK valve in the floor as the tubes are too close together. Knock-off Halkey valves go for 7 quid; I might stick a couple in the sides and leave the lilo plug in the floor.
I put it back in the barn with my other restoration project for a couple of days. When I came back it was limp but not draped over that cabinet like a wet pizza. I pumped up and it stayed firm enough, though I’ve forgotten how mushy an 0.2 bar IK feels. It reminds me why I seriously took the idea of trying to increase the rigidity of my old Sunny before getting other IKs. At the beach I filled it with water and stones – no obvious leaks, (or so I thought). A testament to 40-year-old hypalon and glue.
Have to say too, once pumped up, for an IK the old trout is not bad looking. I think the discreet upsweep of the bow, that plywood ice breaker and slender twin tubes make it look a lot less of a bloat than some. Sea trials to follow.